The difference between VPAT and PAT blade

[Aziz]

Hi

I am a translator, and I have to translate a document containing lots of technical terms.

First of all, there's VPAT (Variable Pitch, Angle & Blade)

Secondly, there's PAT (Power Angle & Blade)

So this site
Variable Pitch Angle Tilt (VPAT) Blade / D6T (EU Stage IIIB) / Medium Track-Type Tractors / Track-Type Tractors / Machines / Our products - Bergerat Monnoyeur
says
A Variable Pitch Angle Tilt (VPAT) blade on the D6T allows the operator to hydraulically adjust the blade lift, angle, and tilt simultaneously, using the ergonomically designed blade control. The operator also has the ability to manually adjust the blade pitch.

This site
What Is a Pat Blade on a Dozer? | eHow
says:
PAT blades are powered to lift, angle and tilt in virtually every desired direction. (...) Most PAT blades operate by use of a joystick located within the dozer cab.

So what's the difference? The only one I see here is that in the first bit, it says "simultaneously", and there's a difference in how it's being done.

Now I could just use the English abbreviation (I've seen other translators do it) but I'm a curious person, and anyway I think using only foreign abbreviations or words in technical field is not helpful, so if I can, I want to give translation as well.

Thank you very much for any clarification in this field

 

[BukitCase]

The main difference is very likely the marketing genius who wrote the copy - his job is often to take two identically designed machines and make one (his company's) look better/more valuable.

Personally, I've only used a couple of machines with a similar feature and they BOTH had a "T" handle control - they were very intuitive to use; moving the handle to the left (inward) tilted blade downward on the left side, to the right moved it downward on the right. Moving the handle forward lowered the blade, and rearward raised it. Twisting the "T" to the left (counter-clockwise) angled the blade left, clock-wise angled it to the right.

The "T" handle had linkages that operated three different hydraulic spool valves depending on which direction the handle was moved, and also how FAR it was moved. As long as you didn't move the lever to maximum in any one axis, you could also move it in another axis and get both to change simultaneously.

The limit to that possibility would depend on the type of hydraulic system - broadly, there are "open center" and "closed center" systems - "open center" means that the pump is continually moving hydraulic fluid thru the system, and all spool valves (when in neutral position) allow fluid to pass thru them and back to the hydraulic reservoir (usually called tank, or "T") - then when you move a lever (actuate a valve) that fluid is re-directed out one of a pair of "work" ports to either push or pull a hydraulic cylinder.

The further you move the lever, the more flow - if you move the lever to the END of its travel, it will normally use ALL available flow - this means that any valve DOWNSTREAM of that one gets NOTHING.

This "variable" lever positioning is typically referred to as "feathering", and is most likely the "V" in your earlier acronym. (It's also the "marketing" part - nearly ALL valves do this, and most operators KNOW this.)

Neither machine I used had the blade "pitch" adjustable, so I'm not familiar with the way that's accomplished unless ONE of those movements uses a separate lever.

More expensive, larger machines sometimes use the more expensive "closed center" valve system - the valves aren't much more expensive, but the pumps are because they are required to "sense" pressure drop, and respond by increasing their output flow. Piping of the system is more expensive too, since each valve gets its own pipe/hose instead of ONE pressure line that runs thru EACH valve in series and then returns to tank.

In these (closed center) systems, all valves can be plumbed in "parallel", so EACH valve has a source of hydraulic pressure ALL the time, and the pump just sends more flow when you open more valves. This allows several circuits to work at nearly full speed at the same time, making the machine faster to respond to multiple operations of the blade, or whatever is being moved.

As to translation, I don't envy you - I used to do this for video recorders a long time ago but I was only re-writing poorly translated Japanese to English for English speaking technicians, most of whom had no second language.

If I had to do what you need, I would probably start by explaining that this "marketing term" came from the English words for what it can do, and then substitute the closest word(s) (in the target language) in its place.

Hopefully your target audience is already familiar with (in this case) heavy equipment, otherwise your copy could get as long-winded as mine

I hope this helps... Steve

 

[Bob Rooks]

Some hydraulic systems will have two pumps stacked together to allow multiple functioning spool valve circuits. Most all dozer controls nowadays are joystick with three or four buttons on top which allows simultaneous functions. The stacked spool valves are linear solenoid actuated, that's where you get the "feathering."
My dozer originally had a "T" handle but I found it awkward for me so I changed it to a three spool joystick with "float" and added another valve for the blade tilt (my dozer also converts to a track loader).
I'm curious what language you are translating to. It might be easier to translate from a language other than English. Foreign manufacturers may have more meaningful nomenclature for you.

 

[tonyoz]

Pitch control on a blade is not new, some larger dozers were fitted with it some 20yrs ago. By rolling the top of the blade forward helps the blade to dig and rolling the blade back allows the tractor to "carry" more dirt over longer distance. VPAT blades are the same as a PAT blade but with the roll feature. As for extra spools to control it may not be necessary if a electric change over valve is used on one of the other functions. That's what Komatsu did on the 155 size and larger tractors

 

[Rustyiron]

Good explanation tonyoz, I also thought that it was just another term for "PAT" until I read your post and was not aware that the "pitch" adjustment is available on a "PAT" blade. :thumbsup:

 

[BukitCase]

Tony, I didn't mean to imply that pitch control was new, only that I'd not seen spool valve setups that could do more than 3 functions on one lever - the machines I ran (briefly, as in rented) were JD 450 and 350's, both had 6-way blades with "T" handles. Coulda used pitch control on those, neither really floated well in "float" mode.

I'm in process of modifying the hydraulics on my older Case 580, adding two diverters to front (grapple and brush trimmer) and at least one to the rear, plus a higher flow motor control circuit - so I'm familiar with the solenoid concept (sorta) -

What I'm NOT familiar with are all the "Buzz" words on larger machines, the last high tonnage machine I ran was a D8 cat in 1955 (I was 10 yrs old at the time) - "state of the art" then was a seat wide enough to take a nap on, a motor to start the motor, and a big long lever you pulled toward you to pull in the cable that wrapped around two triple sheaves holding the blade up - pushing the lever away lowered the blade, and if you REALLY wanted to get yelled at, you let that cable get too slack so it came off the sheaves

I could see where P= pitch, A = Angle, T = Tilt - but why use "V" ? Is that the "variable" achieved by using linear solenoids and variable voltage joysticks, or am I not even on the right planet?

Just curious, I'm a firm believer in the concept that if you're too old to learn you're DEAD... Steve

 

[tonyoz]

Steve, P.A.T stands for Power, Angle, Tilt. The V is another thing as in Variable Pitch. Gees you are just a bit older than me, I operated a D7T for a little while, an all cable machine, 2 drum CCU so it could pull scoops. All the newbys got that tractor and if you didn't look after her you was history PDQ(Pretty Dam Quick). It was in pristine condition. I got moved onto a D7E, hydraulic blade and CCU also pony motor start but no hand cranking. Thought all my xmas's had come at once.

 

[BukitCase]

"no hand cranking" - Yeah, it took me a couple of times (I was 10, remember??!?) to figure out that it actually made a DIFFERENCE which way you wound that knotted rope around the pulley

My next door neighbor at the time was the gyppo logger with the D8, he also had a newer D7. He had a daughter who wasn't interested in anything but horses, so I was kinda the son he never had -

About a year before my "heavy equipment operator training" my dad found a tiny little "dozer", it was about 15 horsepower hand CRANKED (ouch) with a blade and small 3-point, all "over center" controls, no hydraulics - he cleaned it all up and painted it Cat yellow, our neighbor said,"man, that looks like a D-1/2 " - Dad liked that comment so much he cut out a stencil and painted it on both sides of the engine cowl.

We later used that little dozer pulling a slip with a 20 foot cable and landscaped the new house we were building, moved roughly 200 yards of dirt that way. Dad outweighed me by about 100 pounds at the time, so he got to run the slip and I got to drive (10 yrs old and already in heaven :thumbsup: )

Once it's in your blood... Steve